A header for use in a combine harvester includes a cutter bar comprising transversally reciprocating knives for cutting crops at a given height, and an auger or draper mechanism for moving the crops to the centre of the header and from there to the combine's feeder and further on to the crop processing stages in the combine.
In most combines in use today for the harvesting of grain, a single cutter bar is used in the header, cutting the crops at a height of about 10-15 cm from the ground, which means that the grain stalks are harvested together with the grains. The processing of the stalks (threshing, chopping etc), demands a considerable amount of power and negatively affects the capacity of the combine.
One known solution to this problem is the provision of a second cutter bar coupled to the rear of the header and supported by ground engaging roller assemblies, as shown for example in WO-A-2013/011138. This is however quite a complex solution, and the location of the second cutter bar behind the header reduces the available space for using larger wheels and especially tracks on the combine.
WO-A-9853660 shows another header with 2 cutter bars. This solution is however specific for the harvesting of corn, where the stalk portion comprises the valuable crops, and the top portion needs to be prevented from entering the combine. For this reason, the mechanism is very complex involving an upper cutter bar placed forward of the reel and a fixed lower cutter bar. Apart from its complexity, this solution is unsuitable for the harvesting of grain where the top portion of the crop needs to be harvested.
A general problem with any of the existing double cutter bar systems is that the second cutter bar is either a fixed feature of the header or it is described as a modification of an existing header. Switching from a single cutter bar to a double cutter bar therefore requires a replacement of the complete header, or a technical modification of the header, both of which are complex operations.